I liked the suggestion of someone else who floated the idea of an adaptation of The Bloodstone Hunt, with it being a cross of Indiana Jones treasure-hunting and James Bond globetrotting with HYDRA playing spoiler in that chase.

That way you could use another traditional Cap villain like Zemo and potentially expand on Crossbones as adversaries who stand in his way. It's hard to say, but from all the positive buzz surrounding TWS, I have complete faith in the Russos to nail the third installment too.